The present invention relates generally to fluid treatment systems, such as water treatment systems including water softeners, and more particularly to a system and method for controlling multiple sized water softener tanks. It is recognized that many aspects of the present invention can be applied to other types of fluid treatment systems, such as filtering or de-ionizing systems.
Water softeners are known and typically include a raw water source, a treatment tank containing an ion exchange resin, a brine tank containing a brine solution, and a control valve for directing fluids between the source, the tanks and a drain or other output.
Water softening occurs by running water through the ion exchange resin, which replaces the calcium and magnesium cations in the water with sodium cations. As the ion exchange process continues, the resin eventually loses its capacity to soften water and must be replenished with sodium cations. The process by which the calcium and magnesium ions are removed, the capacity of the ion exchange resin to soften water is restored, and the sodium ions are replenished is known as regeneration.
Water treatment systems in homes typically include one treatment tank and one brine tank to handle the relatively low water flow. Larger commercial treatment systems include multiple water softening units (at least one treatment tank and brine tank) to handle the larger volume of water that passes through these systems. The water softening units are connected together such that the plumbing through each of the individual systems is in parallel with the plumbing of the other systems. Each of the plumbing paths includes a control valve that is used to selectively turn a particular branch or path “on” or “off.” This allows a user to be able to control the number of the water softening units that are in operation at a given time based on demand for water.
Commercial size treatment systems typically include a centralized controller that continuously monitors the water flow demand and determines the appropriate number of the paths to turn “on” or “off” to service the current demand. A “trip” level flow rate is the maximum flow that a system is designed to handle through each of the paths. By monitoring the total flow rate and dividing it by the trip level flow rate, the controller determines the exact number of units that need to be turned “on.” Typically, the treatment tanks in such systems are designed to be the same size so that each tank can handle the same “trip” level amount of water flow.
A problem occurs in such systems when there is a relatively low water flow. Specifically, if the water flows too slowly through a resin bed in the brine tank for an extended period of time, “channeling” may occur. Channeling causes the water flow to be unevenly distributed throughout the resin bed, resulting in only a portion of the resin being exposed to the water flow, with the remainder being bypassed. As a result, the resin along the channel becomes exhausted and then allows untreated water to pass through the treatment system.